Ion-conducting polymeric materials

ABSTRACT

A method of preparing an ion-conducting polymeric material, for example, for a fuel cell, in a desired form (hereinafter “said formed polymeric material”), comprises: (i) selecting a first ion-conducting polymeric material; (ii) selecting a solvent formulation which can dissolve said first ion-conducting polymeric material, wherein said formulation includes a first solvent part which is water; (iii) preparing a composite formulation in a process which includes dissolving first ion-conducting polymeric material in said solvent formulation; (iv) forming said composite formulation into a desired form; (v) providing conditions for removal of said solvent formulation from said form described in (iv) thereby to prepare said formed polymeric material. The first ion-conducting polymeric material preferably includes polyaryletherketone units. Said solvent formulation preferably includes a second solvent part selected from acetone, tetrahydrofuran and acetone.

This application is the U.S. National Phase of International ApplicationPCT/GB02/04250, filed 18 Sep. 2002, which designated the U.S.

This invention relates to ion-conducting polymeric materials andparticularly, although not exclusively, relates to a method of preparingsuch materials. Preferred embodiments relate to the preparation ofcrystalline ion-conducting polymeric materials for fuel cells, forexample polymer electrolyte membranes thereof.

One type of polymer electrolyte membrane fuel cell (PEMFC), shownschematically in FIG. 1 of the accompanying diagrammatic drawings, maycomprise a thin sheet 2 of a hydrogen-ion conducting Polymer ElectrolyteMembrane (PEM) sandwiched on both sides by a layer 4 of platinumcatalyst and an electrode 6. The layers 2, 4, 6 make up a MembraneElectrode Assembly (MEA) of less than 1 mm thickness.

In a PEMFC, hydrogen is introduced at the anode (fuel electrode) whichresults in the following electrochemical reaction:Pt-Anode (Fuel Electrode) 2H₂→4H⁺+4e⁻

The hydrogen ions migrate through the conducting PEM to the cathode.Simultaneously, an oxidant is introduced at the cathode (oxidantelectrode) where the following electrochemical reaction takes place:Pt-Cathode (Oxidant Electrode) O₂+4H⁺+4e⁻→2H₂O

Thus, electrons and protons are consumed to produce water and heat.Connecting the two electrodes through an external circuit causes anelectrical current to flow in the circuit and withdraw electrical powerfrom the cell.

Preferred ion-conducting polymeric materials for use as components ofpolymer electrolyte membranes in fuel cells have high conductivity (lowEW, or high ion-exchange capacities), optimum water uptake for goodconductivity and mechanical properties and solubility in solvents whichcan be used to cast the membranes.

Examples of known ion-conducting polymeric materials are described inU.S. Pat. No. 5,985,477 (Sumitomo) and U.S. Pat. No. 5,906,716(Hoechst). The polyaryletherketones and/or sulphones described aredissolved in a solvent, usually N-methylpyrrolidone (NMP), and are thencast to prepare membranes. It should be noted that the polymer initiallydissolved in the solvent is the same, in terms of its physical and/orchemical properties, both before and after casting—casting is used onlyto form the polymer into a predetermined, desired shape, for example athin membrane.

Whilst NMP is a very good solvent for casting membranes from a widerange of materials, membranes cast from NMP (especially polymerelectrolyte membranes of fuel cells) can have defects and/or exhibitproblems in downstream process steps. Thus, a first object of a firstembodiment of the present invention is to address problems associatedwith the use of NMP as a solvent for casting membranes.

A second object of the present invention is to provide an improvedprocess for the preparation of polymeric materials in a desired form,particularly ion-conducting polymeric materials, for example for polymerelectrolyte membranes and/or gas diffusion electrodes.

According to a first aspect of the invention, there is provided a methodof preparing an ion-conducting polymeric material in a desired form(hereinafter “said formed polymeric material”), the method comprising:

-   (i) selecting a first ion-conducting polymeric material;-   (ii) selecting a solvent formulation which can dissolve said first    ion-conducting polymeric material, wherein said formulation includes    a first solvent part which is water;-   (iii) preparing a composite formulation in a process which includes    dissolving first ion-conducting polymeric material in said solvent    formulation;-   (iv) forming said composite formulation into a desired form;-   (v) providing conditions for removal of said solvent formulation    from said form described in (iv) thereby to prepare said formed    polymeric material.

Unless otherwise stated in this specification, a phenyl moiety may have1,4- or 1,3-, especially 1,4-, linkages to moieties to which it isbonded.

Said solvent formulation in which said first ion-conducting polymericmaterial is dissolved preferably includes a second solvent part. Saidsecond solvent part is preferably an organic solvent. Said secondsolvent part preferably has a boiling point at atmospheric pressure ofgreater than −30° C., preferably greater than 0° C., more preferablygreater than 10° C., especially greater than 20° C. The boiling pointmay be less than 200° C., preferably less than 150° C., especially lessthan 120° C. Said second solvent part is preferably able to form adipole-dipole interaction with the first polymeric material. In thisregard, the first polymeric material suitably acts as a soft Lewis baseand the second solvent part may then act as a Lewis acid. Said secondsolvent part may include a ketone, ether or haloalkyl (especiallychloro- or fluoroalkyl) group or an unsaturated ring structure. Saidsecond solvent part preferably includes less than eight, preferably lessthan seven, carbon atoms. Where said second solvent part includes aketone, ether or haloalkyl group, said second solvent part may includeless than six carbon atoms. Said second solvent part may be aliphatic.For example, it may be an alkylhalide, ketone or amide solvent.Alternatively, said second solvent part may be a non-aromatic cyclicsolvent. For example it may be a cyclic ether or cyclic ketone solvent.Said second solvent part may be aromatic, for example it may be anoptionally-substituted, especially an optionally monosubstituted,benzene. Said second solvent part is preferably aprotic. It may be apolar aprotic solvent. Said second solvent part may be selected frombenzene, toluene, dichloromethane, tetrahydrofuran, cyclopentanone,acetone, 1,3-dichloropropane, chlorobenzene, tetrafluoroethane,diethylketone, methylethyl ketone, cyclohexanone and ethylbenzene.Preferred such solvents include acetone, tetrahydrofuran (THF) anddichloromethane. Of the aforesaid, acetone may be especially preferred.

Said first polymeric material suitably has a solubility of at least 2%w/w, preferably at least 4% w/w, more preferably at least 7.5% w/w, insaid solvent formulation at the boiling point of said solventformulation.

Suitably, in the method, at least 2% w/w, preferably at least 4% w/w,more preferably at least 7.5% w/w of said first polymeric material isdissolved in said solvent formulation.

Suitably, in the method, the total amount of polymeric materials(including said first polymeric material and any polymeric materialblended therewith) dissolved in said solvent formulation is at least 2%w/w, preferably at least 5% w/w, more preferably at least 7.5% w/w. Thetotal amount may be 30% w/w or less.

In the method, said composite formulation may be formed into a desiredform (e.g. cast) at a temperature at or below the boiling point of saidsolvent formulation.

A preferred first ion-conducting polymeric material is one having amoiety of formula

and/or a moiety of formula

and/or a moiety of formula

wherein at least some of the units I, II and/or III are funtionalized toprovide ion-exchange sites, wherein the phenyl moieties in units I, II,and III are independently optionally substituted and optionallycross-linked; and wherein m,r,s,t,v,w and z independently represent zeroor a positive integer, E and E′ independently represent an oxygen or asulphur atom or a direct link, G represents an oxygen or sulphur atom, adirect link or a —O-Ph-O— moiety where Ph represents a phenyl group andAr is selected from one of the following moieties (i)* or (i) to (x)which is bonded via one or more of its phenyl moieties to adjacentmoieties

In (i)*, the middle phenyl may be 1,4- or 1,3-substituted.

Suitably, to provide said ion exchange sites, said s polymeric materialis sulphonated, phosphorylated, carboxylated, quaternary-aminoalkylatedor chloromethylated, and optionally further modified to yield —CH₂PO₃H₂,—CH₂NR₃ ²⁰⁺ where R²⁰ is an alkyl, or —CH₂NAr₃ ^(x+) where Ar^(x) is anaromatic (arene), to provide a cation or anion exchange membrane.Further still, the aromatic moiety may contain a hydroxyl group whichcan be readily elaborated by existing methods to generate —OSO₃H and—OPO₃H₂ cationic exchange sites on the polymer. Ion exchange sites ofthe type stated may be provided as described in WO95/08581.

Preferably, said first material is sulphonated. Preferably, the onlyion-exchange sites of said first material are sites which aresulphonated.

References to sulphonation include a reference to substitution with agroup —SO₃M wherein M stands for one or more elements selected with dueconsideration to ionic valencies from the following group: H, NR₄ ^(y+),in which R^(y) stands for H, C₁–C₄ alkyl, or an alkali or alkaline earthmetal or a metal of sub-group 8, preferably H, NR₄ ⁺, Na, K, Ca, Mg, Fe,and Pt. Preferably M represents H. Sulphonation of the type stated maybe provided as described in WO96/29360.

Said first polymeric material may include more than one different typeof repeat unit of formula I; more than one different type of repeat unitof formula II; and more than one different type of repeat unit offormula III.

Said moieties I, II and III are suitably repeat units. In the firstpolymeric material, units I, II and/or III are suitably bonded to oneanother—that is, with no other atoms or groups being bonded betweenunits I, II, and III.

Where the phenyl moieties in units I, II or III are optionallysubstituted, they may be optionally substituted by one or more halogen,especially fluorine and chlorine, atoms or alkyl, cycloalkyl or phenylgroups. Preferred alkyl groups are C₁₋₁₀, especially C₁₋₄, alkyl groups.Preferred cycloalkyl groups include cyclohexyl and multicyclic groups,for example adamantyl. In some cases, the optional substituents may beused in the cross-linking of the polymer. For example, hydrocarbonoptional substituents may be functionalised, for example sulphonated, toallow a cross-linking reaction to take place. Preferably, said phenylmoieties are unsubstituted.

Another group of optional substituents of the phenyl moieties in unitsI, II or III include alkyls, halogens, C_(y)F_(2y+1) where y is aninteger greater than zero, O—R^(q) (where R^(q) is selected from thegroup consisting of alkyls, perfluoralkyls and aryls), CF═CF₂, CN, NO₂and OH. Trifluormethylated phenyl moieties may be preferred in somecircumstances.

Where said first polymeric material is cross-linked, it is suitablycross-linked so as to improve its properties as a polymer electrolytemembrane, for example to reduce its swellability in water. Any suitablemeans may be used to effect cross-linking. For example, where Erepresents a sulphur atom, cross-linking between polymer chains may beeffected via sulphur atoms on respective chains. Alternatively, saidpolymer may be cross-linked via sulphonamide bridges as described inU.S. Pat. No. 5,561,202. A further alternative is to effectcross-linking as described in EP-A-0008895.

Where w and/or z is/are greater than zero, the respective phenylenemoieties may independently have 1,4- or 1,3-linkages to the othermoieties in the repeat units of formulae II and/or III. Preferably, saidphenylene moieties have 1,4-linkages.

Preferably, the polymeric chain of the first material does not include a—S— moiety. Preferably, G represents a direct link.

Suitably, “a” represents the mole % of units of formula I in said firstpolymeric material, suitably wherein each unit I is the same; “b”represents the mole % of units of formula II in said material, suitablywherein each unit II is the same; and “c” represents the mole % of unitsof formula III in said material, suitably wherein each unit III is thesame. Preferably, a is in the range 45–100, more preferably in the range45–55, especially in the range 48–52. Preferably, the sum of b and c isin the range 0–55, more preferably in the range 45–55, especially in therange 48–52. Preferably, the ratio of a to the sum of b and c is in therange 0.9 to 1.1 and, more preferably, is about 1. Suitably, the sum ofa, b and c is at least 90, preferably at least 95, more preferably atleast 99, especially about 100. Preferably, said first polymericmaterial consists essentially of moieties I, II and/or III.

Said first polymeric material may be a homopolymer having a repeat unitof general formula

or a homopolymer having a repeat unit of general formula

or a random or block copolymer of at least two different units of IVand/or V provided that repeat units (or parts of repeat unit) arefunctionalised to provide ion-exchange sites;

wherein A, B, C and D independently represent 0 or 1 andE,E′,G,Ar,m,r,s,t,v,w and z are as described in any statement herein.

As an alternative to a polymer comprising units IV and/or V discussedabove, said first polymeric material may be a homopolymer having arepeat unit of general formula

or a homopolymer having a repeat unit of general formula

or a random or block copolymer of at least two different units of IV*and/or V* provided that repeat units (or parts of repeat units) arefunctionalised to provide ion-exchange sites; wherein A, B, C, and Dindependently represent 0 or 1 S and E, E′, G, Ar, m, r, s, t, v, w andz are as described in any statement herein.

Preferably, m is in the range 0–3, more preferably 0–2, especially 0–1.Preferably, r is in the range 0–3, more preferably 0–2, especially 0–1.Preferably t is in the range 0–3, more preferably 0–2, especially 0–1.Preferably, s is 0 or 1. Preferably v is 0 or 1. Preferably, w is 0or 1. Preferably z is 0 or 1.

Preferably Ar is selected from the following moieties: (xi)* and (xi) to(xxi):

In (xi)*, the middle phenyl may be 1,4- or 1,3-substituted.

Preferably, (xv) is selected from a 1,2-, 1,3-, or a 1,5-moiety; (xvi)is selected from a 1,6-, 2,3-, 2,6- or a 2,7-moiety; and (xvii) isselected from a 1,2-, 1,4-, 1,5-, 1,8- or a 2,6-moiety.

Preferably, said first ion-conducting polymeric material is crystallineor crystallisable.

Unless otherwise stated in this specification, a reference to acrystalline material extends to any material having at least somecrystallinity.

The existence and/or extent of crystallinity in a polymer is preferablymeasured by wide angle X-ray diffraction, for example as described byBlundell and Osborn (Polymer 24, 953, 1983). Alternatively, DifferentialScanning Calorimetry (DSC) could be used to assess crystallinity. Thelevel of crystallinity in said first polymeric material may be 0% (e.g.where the material is amorphous or crystallisable); or the level ofcrystallinity may be at least 0.5%, suitably at least 1%, preferably atleast 5% weight fraction, suitably when measured as described byBlundell and Osborn. The level of crystallinity in said first polymericmaterial may be less than 20%.

In a preferred embodiment, said first ion-conducting polymeric materialis crystalline or crystallisable and a solvent formulation is selectedin step (ii) which can dissolve said first polymeric material andincrease its crystallinity. In this case, it is possible to adjustadvantageously the properties of polymeric materials for ion-conductingmembranes by selection of appropriate casting solvents thereby toproduce membranes having improved properties compared to the materialswhen cast using processes described in the prior art. Furthermore, theimprovement in properties can be achieved without any additionaltreatment step compared to known processes.

The difference between the level of crystallinity (%), suitably measuredas described above, in said formed polymeric material and the level ofcrystallinity (%) in said first ion-conducting polymeric material priorto dissolution in said solvent formulation is suitably at least 0.1%,preferably at least 0.3%, more preferably at least 0.4%, especially atleast 0.5%. In some cases, the difference may be 1%, 2% or even 5%.

The difference between the level of crystallinity (%) in said formedpolymeric material and the level of crystallinity (%) of material formedin identical fashion to that of said formed material except that asolvent formulation, for example comprising NMP, is used which whilstcapable of dissolving said first polymeric material is not capable ofincreasing its crystallinity, may be at least 0.1%, preferably at least0.4%, more preferably at least 1%, especially at least 3%.

The difference between the sensitivity (or water uptake) (%) of saidformed polymeric material compared to that of a material formed in anidentical fashion to that of said formed material except that a solventformulation, for example NMP, is used which whilst capable of dissolvingsaid first polymeric material is not capable of increasing itscrystallinity may be at least 20%, preferably at least 40%, morepreferably at least 60%, especially at least 80%.

When said first polymeric material has at least some crystallinity or iscrystallisable, the material may be made up of a number of repeat units,some of which may be crystallisable or have some crystallinity and someof which may be amorphous. For example, repeat units provided withion-exchange sites, for example sulphonate groups, will tend to beamorphous, as will repeat units which include bulky groups or —SO₂—.Repeat units which are crystalline or crystallisable suitably includemoieties which can be exchanged with ether units in a polyetherketonecrystal lattice. Ketone units and/or —S— units may be exchanged and may,therefore, be components of crystalline or crystallisable units.

Said first ion-conducting polymeric material preferably includes a firstcrystalline or crystallisable repeat unit which suitably includes phenylmoieties linked by —CO— and/or -Q- groups, where Q represents —O— or—S—, but does not include —SO₂— and/or any groups whose shape and/orconformation is/are incompatible with the crystalline conformationadopted by polyetherketone units. Said first polymeric material mayadditionally include a second ion-conducting repeat unit having phenylmoieties; carbonyl or sulphone moieties; and ether or thioether moietiesin the polymer backbone. Such a unit may be functionalised to provideion-exchange sites and will, therefore, suitably be amorphous.Optionally, said first polymeric material may include a third amorphousrepeat unit which is not functionalised to provide ion-exchange sitesbut is amorphous. Said third repeat unit may include —SO₂— and/or anygroups whose shape and/or conformation is/are incompatible with thecrystalline conformation adopted by polyetherketone units.

A said first crystalline or crystallisable ion-conducting polymericmaterial may includes moieties I, II and/or III described above,provided said material includes crystalline or crystallisable units.Said first polymeric material may be a homopolymer or copolymer whichincludes units IV, V, IV*, V* as described above, provided thatrespective repeat units (or parts of repeat units) of said material arecrystalline or crystallisable and other repeat units (or parts of repeatunits) are functionalised to provide ion-exchange sites.

Said first ion-conducting polymeric material may include:

-   -   a said first crystalline or crystallisable unit which is of        general formula IV, IV*, V or V* as described above, provided        said unit is crystalline or crystallisable. Suitably, to be        crystalline or crystallisable, said first unit does not include        any Ar group of formula (ii), (viii), (ix) or (x). More        preferably, it may also not include an Ar group of formula        (v), (vi) or (vii). Preferred Ar groups consist of one or more        phenyl groups optionally in combination with one or more        carbonyl and/or ether groups.    -   a said second ion-exchange unit of formula IV, V, IV* or V* as        described above, wherein said ion-exchange unit includes        ion-exchange sites.    -   a said third amorphous unit which is of general formula IV, IV*,        V or V*, provided, however, that said unit includes at least        some moieties whose shape and/or conformation is/are        incompatible with the crystalline conformation of said first        crystalline unit so that said third unit is amorphous.        Preferably, said third unit includes an —SO₂— moiety, a bulky        group and/or a moiety of formula -Q-Z-Q- wherein Z represents an        aromatic group containing moiety and Q is as described above,        wherein said unit of formula -Q-Z-Q- is not symmetrical about an        imaginary line which passes through the two -Q- moieties        provided, however, that said unit is not derived from        dihydroxybenzophenone substituted by groups Q at the 4- and        4′-positions (since such a benzophenone acts in the manner of a        symmetrical moiety by virtue of the carbonyl group being        substantially similar to an ether group thereby allowing the        carbonyl group to be interchanged with an ether group in a        polyaryletherketone crystal lattic).

Examples of units of formula -Q-Z-Q- (especially wherein Q is —O—) areas follows:

One preferred class of first polymeric materials may include at leastsome ketone moieties in the polymeric chain. In such a preferred class,the polymer preferably does not only include —O— and —SO₂— moietiesbetween aryl (or other unsaturated) moieties in the polymeric chain.Thus, in this case, suitably, a polymer of the first aspect does notconsist only of moieties of formula III, but also includes moieties offormula I and/or II.

One preferred class of first polymeric materials does not include anymoieties of formula III, but suitably only includes moieties of formulaeI and/or II. Where said first polymeric material is a homopolymer orrandom or block copolymer as described, said homopolymer or copolymersuitably includes a repeat unit of general formula IV. Such a polymermay, in some embodiments, not include any repeat unit of general formulaV.

Suitable moieties Ar are moieties (i)*, (i), (ii), (iv) and (v) and, ofthese, moieties (i)*, (i), (ii) and (iv) are preferred. Preferredmoieties. Ar are moieties (xi)*, (xi), (xii), (xiv), (xv) and (xvi) and,of these, moieties (xi)*, (xi), (xii) and (xiv) are especiallypreferred. Another preferred moiety is moiety (v), especially, moiety(xvi). In relation, in particular to the alternative first polymericmaterials comprising units IV* and/or V*, preferred Ar moieties are (v)and, especially, (xvi).

Said first crystalline or crystallisable unit preferably only includesphenyl groups linked by —CO— and —O—.

Said second ion-exchange unit preferably includes a unit which, prior tofunctionalisation with ion-exchange sites (e.g. prior to sulphonation),is electron-rich and relatively non-deactivated. Examples include-Q-phenyl-Q-, -Q-biphenyl-Q- and -Q-naphthalene-Q- where Q represents anoxygen or sulphur atom, especially an oxygen atom. Such units can beprovided with ion-exchange sites (e.g. sulphonated) under relativelymild conditions as described in the examples hereinafter. Under the sameconditions the first units are not provided with ion-exchange sites(e.g. sulphonated). Thus, suitably, up to 100 mole % of phenyl groups insaid second ion-exchange unit are sulphonated.

Said optional third unit preferably includes phenyl groups linked by—CO, —SO₂—, —O— and/or —S— provided said third unit is not provided withion-exchange sites (e.g. sulphonated) under the relatively mildconditions under which said second unit is functionalised (i.e. saidthird unit is less easy to provide with ion-exchange sites compared tosaid second unit prior to its functionalisation as described) andprovided said third unit is amorphous.

Said first crystalline or crystallisable unit described above maycomprise phenyl groups linked by ether and ketone groups. Said unit maybe a repeat unit of formula

wherein n1, n2, n3 and n4 independently represent 0 or 1 provided thatthe sum of n1, n2, n3 and n4 is at least 2 and that when n2 is 1 atleast one of n3 and n4 is 1. Preferred first units are:ether-phenyl-ketone-phenyl-ether-phenyl-ketone-phenyl (i.e. n1=0, n2=1,n3=1, n4=0),ether-phenyl-ketone-phenyl-ketone-phenyl-ether-phenyl-ketone-phenyl-ketone-phenyl(i.e. n1=n2=n3=n4=1) andether-phenyl-ketone-phenyl-ether-phenyl-ketone-phenyl-ketone-phenyl (ien1=0, n2=n3=n4=1).

Said second ion-conducting unit may be of formula

wherein IEU refers to a unit which incorporates ion-exchange sites (e.g.it is sulphonated) and n⁵, n⁶ and n⁷ represent 0 or 1 provided that thesum of n⁵, n⁶ and n⁷ is at least 1. Preferably, IEU is a phenyl,biphenyl or di-substituted naphthalene group provided with ion-exchangesites. Preferred second units are:-ether-IEU-ether-phenyl-sulphone-phenyl-(i.e. n⁵ is 1, n⁶=n⁷=0),-ether-IEU-ether-phenyl-ketone-phenyl-(i.e. n⁵=0, n⁶=1, n⁷=0) and-ether-IEU-ether-phenyl-ketone-phenyl-ketone (i.e. n⁵=0, n⁶=n⁷=1)wherein IEU represents any of the moieties described above.

Preferred optional third units are of general formula—O-Ph-(SO₂-Ph)_(n8)-(CO-Ph)_(n9)-[AMOR]-  XVIIIwherein n⁸ is 0 or 1, n⁹ is 0, 1 or 2 and AMOR represents an amorphousunit, for example of formulae:

The phenyl groups of the third unit of formula XVIII may be 1,3- or1,4-substituted by the groups shown. Preferably, they are1,4-substituted.

Preferred third units are: ether-phenyl-sulphone-phenyl-AMOR-(i.e. n⁸=1,n⁹=0 in formula XVIII), -ether-phenyl-ketone-phenyl-ketone-AMOR-(i.e.n⁸=0, n⁹=2), -ether-phenyl-ketone-phenyl-AMOR-(i.e. n⁸=0, n⁹=1) whereinAMOR represents moieties IXX, XX or XXI, especially IXX or XX.

Copolymers may be prepared having one or more first repeat units and oneor more of said second repeat units.

Where said first polymeric material is a copolymer as described, themole % of co-monomer units, for example said first and second repeatunits described above, may be varied to vary the solubility of thematerial in solvent formulations that may be used in the preparation ofsaid formed polymeric material and/or in other solvents, especiallywater. Also, the mole % of co-monomer units may be varied to vary thelevel of crystallinity and/or crystallisability. For homopolymers, thelevel of crystallinity and/or crystallisability may be determined by thelevel of functionalisation with ion-exchange sites.

Where a phenyl moiety is sulphonated, it may only be mono-sulphonatedand this is preferred. However, in some situations it may be possible toeffect bi- or multi-sulphonation.

Suitably “A*” represent the mole % of said first crystalline orcrystallisable units in said first ion-conducting polymeric material;“B*” represents the mole % of said second ion-exchange units; and “C*”represents the mole % of said third amorphous units.

A* is preferably at least 5 and may be at least 10. It is preferablyless than 70, more preferably less than 60, especially less than 40. B*is suitably at least 10, preferably at least 20, more preferably atleast 30. It is preferably less than 70, more preferably less than 60,especially less than 50. C* is suitably at least 50, preferably at least10, more preferably at least 20, especially at least 30. It may be lessthan 80, preferably less than 70.

The glass transition temperature (T_(g)) of said first ion-conductingpolymeric material may be at least 144° C., suitably at least 150° C.,preferably at least 154° C., more preferably at least 160° C.,especially at least 164° C. In some cases, the Tg may be at least 170°C., or at least 190° C. or greater than 250° C. or even 300° C.

Said first polymeric material may have an inherent viscosity (IV) of atleast 0.1, suitably at least 0.3, preferably at least 0.4, morepreferably at least 0.6, especially at least 0.7 (which corresponds to areduced viscosity (RV) of least 0.8) wherein RV is measured at 25° C. ona solution of the polymer in concentrated sulphuric acid of density 1.84gcm⁻³, said solution containing 1 g of polymer per 100 cm⁻³ of solution.IV is measured at 25° C. on a solution of polymer in concentratedsulphuric acid of density 1.84 gcm³, said solution containing 0.1 g ofpolymer per 100 cm³ of solution. The measurements of both RV and IV bothsuitably employ a viscometer having a solvent flow time of approximately2 minutes.

The equivalent weight (EW) of said ion-conductive polymeric material ispreferably less than 850 g/mol, more preferably less than 800 g/mol,especially less than 750 g/mol. The EW may be greater than 300, 400 or500 g/mol.

The boiling water uptake of ion-conductive polymeric material measuredas described hereinafter is suitably less than 350%, preferably lessthan 300%, more preferably less than 250%.

The main peak of the melting endotherm (Tm) for said first polymericmaterial may be at least 300° C.

When said first polymeric material has at least some crystallinity or iscrystallisable, said solvent formulation selected in step (ii) of themethod suitably comprises a said second solvent part which is adapted toincrease the crystallinity of said first polymeric material and suitablyis able to do this independently of the presence of said first solventpart. For example, said first polymeric material in solid form may beimmersed in said second solvent part whereupon after a period, itscrystallinity may be increased. Water in said solvent formulationsuitably is adapted to improve the ability of the solvent formulation todissolve said first polymeric material compared to a case wherein saidsolvent formulation comprises said second solvent part alone. Water isnot, however, adapted to increase the crystallinity of said firstpolymeric material in the manner described for said second solvent part.

Said solvent formulation may include further solvent parts. For example,it may include a third (and possibly other) solvent part(s) which mayhave any feature of said second solvent part. Preferably, however, saidsolvent formulation only includes a single solvent adapted to increasethe crystallinity as described.

Said composite formulation may include a fourth solvent part. A saidfourth solvent part may be part of the composite formulation in whichthe first ion-conducting polymeric material is dissolved or may be addedto the composite formulation after said first ion-conducting polymericmaterial has been dissolved therein. Said fourth solvent part issuitably selected to optimise the formation and/or properties of saidformed polymeric material. For example, when said formed polymericmaterial is a film, it may optimise formation of a unitary, smooth film.Said fourth solvent may have a plasticizing effect. Examples of suitablefourth parts are NMP and dimethylacetamide (DMAC).

The identity of said solvent formulation, the identity and/or relativeamounts of said first and second solvent parts, the temperature and/orpressure at which said first polymeric material is dissolved in saidsolvent formulation and/or the amount of said first polymeric materialto be dissolved may be selected according to the identity of said firstpolymeric material and/or (for crystalline or crystallisable materials)the level of its inherent crystallinity before dissolution and/or theextent to which it is desired to increase its level of crystallinity.

If, for example, a first polymeric material selected has relatively lowinherent solubility in said second solvent part, then more of said firstsolvent part may be included in said solvent formulation to provide asatisfactory concentration of said first polymeric material dissolved insaid solvent formulation. If, for example, said first polymeric materialis an amorphous (optionally crystallisable) polymer then the solubilityin said second solvent part may be higher (compared to a similarpolymeric material having a higher level of crystallinity) and,accordingly, it may be possible to include a greater amount of saidsecond solvent part in said formulation and the presence of such agreater amount may facilitate obtaining a relatively large difference inthe crystallinity of said formed polymeric material compared to that ofsaid first polymeric material when said first polymeric material iscrystalline/crystallisable. Also, in general terms, the ratio of theamounts of first and second solvent parts may be varied to allow firstpolymeric materials of a range of crystallinities to be dissolved insaid solvent formulation.

The ratio of the volume of said first solvent part to the volume of saidsecond solvent part in said solvent formation is suitably in the range0.2 to 5, preferably in the range 0.4 to 2.0, especially in the range0.5 to 1.5.

The % v/v of said first solvent part in said solvent formulation ispreferably at least 10% v/v, more preferably at least 20% v/v. In someembodiments, the % v/v may be at least 30% v/v. Suitably, the % v/v isless than 90% v/v, preferably less than 80% v/v, more preferably lessthan 70% v/v, especially less than 65% v/v. In some cases, the % v/v maybe less than 60% v/v.

The % v/v of said second solvent part is suitably at least 10% v/v,preferably at least 25% v/v, more preferably at least 35% v/v,especially at least 40% v/v.

Said solvent formulation may include 0 to 30% v/v, preferably 0 to 25%v/v of a said third solvent part.

When said composite formulation includes a fourth solvent part, the %v/v of said fourth solvent part in said composite formulation may be inthe range 0 to 10% v/v, preferably 0 to 7.5% v/v, especially 0 to 5%v/v.

Preferably, said composite formulation includes 10% v/v or less, morepreferably 7.5% or less, especially 5% or less of NMP.

In the method, said composite formulation may include other dissolved ordispersed components. For example, said first polymeric material,together with one or more other polymeric materials may be dissolved insaid solvent formulation to prepare said composite formulation. Said oneor more other polymeric materials may be selected from ion-conductingpolymeric materials which may be amorphous or crystalline/crystallisableand may have any feature of said first ion-conducting polymeric materialdescribed or may be non-conducting polymeric materials and/or amorphouspolymeric materials. Suitably at least 50wt %, preferably at least 70wt%, more preferably at least 85wt %, especially at least 95wt % of thetotal of polymeric materials dissolved in said solvent formulation toprepare said composite formulation is comprised of said firstion-conducting polymeric material. Preferably, the only ion-conductingpolymeric material (preferably the only polymeric material) dissolved insaid solvent formulation is said first polymeric material.

Said desired form of said formed polymeric material is preferably apredetermined form suitably having a predetermined shape. Said desiredform preferably comprises a part of an ion-conducting component forexample an ion-conducting membrane or electrode, for example gasdiffusion electrode, of a fuel cell. Said first polymeric material ispreferably formed into said desired form in a process which includes thestep of casting said first polymeric material in said solventformulation.

A membrane which comprises, preferably consists essentially of, saidformed polymeric material may be formed in the method. In this case,therefore, said membrane comprises a unitary material which may define,for example, a PEM of a fuel cell or electrolyser. In a subsequent step,a catalyst material may be contacted with said membrane on both sidesthereof. Alternatively, said formed polymeric material may be a part ofa composite membrane, for example a composite ion-conducting membrane.

In the method, said formed polymeric material may be associated with acomposite membrane material to form a composite membrane in a variety ofways. For example, said formed polymeric material in the form of anunsupported conductive polymer film can be contacted with, for examplelaminated to, a said composite membrane material. Alternatively (andpreferably), one of either said composite membrane material or saidformed polymeric material may be impregnated with the other one ofeither said composite membrane material or said formed polymericmaterial.

Said composite membrane material may be a support material forsupporting said formed polymeric material. In this case, said compositemembrane material preferably is stronger and/or has a lower waterabsorbance compared to said formed polymeric material.

Alternatively, said formed polymeric material may be a support for thecomposite membrane material.

Examples of composite membrane materials include:

-   (A) materials comprising or, preferably consisting essentially of,    polytetrafluoroethylene, suitably provided as a porous film. Such a    support material may be as described in accordance with WO97/25369    and WO96/28242 and the contents of the aforementioned documents as    regards the polytetrafluoroethylene are incorporated herein by    reference; and surface modified polytetrafluoro-ethylene.-   (B) optionally-substituted polyolefins, especially    optionally-substituted polypropylene or polyethylene and copolymers    of any of the aforesaid.-   (C) Lyotropic liquid crystalline polymers, such as a polybenzazole    (PBZ) or polyaramid (PAR or Kevlar®) polymer. Preferred    polybenzazole polymers include polybenzoxazole (PBO),    polybenzothiazole (PBT) and polybenzimidazole (PBI) polymers.    Preferred polyaramid polymers include polypara-phenylene    terephthalamide (PPTA) polymers. Structures of the above-mentioned    polymers are listed in Table 4 of WO99/10165, the contents of which    are incorporated herein by reference.-   (D) Polysulfone (PSU), polyimide (PI), polyphenylene oxide (PPO),    polyphenylene sulphoxide (PPSO), polyphenylene sulphide (PPS),    polyphenylene sulphide sulphone (PPS/SO₂), polyparaphenylene (PPP),    polyphenylquinoxaline (PPQ), polyarylketone, polyethersulphone (PES)    and polyetherketone and polyetheretherketone polymers, for example    PEK™ polymers and PEEK™ polymers respectively from Victrex Plc.-   (E) Polymers having moieties I, II and/or III and/or preferred    repeat units IV, IV*, V and V*, as described above for said first    polymeric material, except that such polymers may be crystallisable,    crystalline or amorphous and may not be functionalised to provide    ion-exchange sites.-   (F) Polymers described in (E), wherein at least some units I, II    and/or III are functionalized to provide ion-exchange sites suitably    of a type described herein with reference to said first polymeric    material.-   (G) Polymers described in (D) which are functionalized, especially    sulphonated, to provide ion-exchange sites, as described in    WO99/10165.-   (H) Perfluorinated ionomers, for example carboxyl-, phosphonyl- or    sulphonyl-substituted perfluorinated vinyl ethers as described in    WO99/10165. An especially preferred example is NAFION (Trade Mark)—a    perfluorosulphonate ionomer described in Journal of Electrochemical    Society, Vol 132, pp 514–515 (1985).-   (I) Ion-conductive polymers comprising α,β,β-trifluorostyrene    monomeric units as described in WO97/25369, the content of which is    incorporated herein by reference.-   (J) Ion-conducting polymers comprising polystyrene sulphonic acid    (PSSA), polytrifluorostyrene sulphonic acid, polyvinyl phosphonic    acid (PVPA), polyvinyl carboxylic (PVCA) acid and polyvinyl    sulphonic acid (PVSA) polymers, and metals salts thereof.

When the composite membrane material is not an ion-conducting materialit preferably acts as a support for said formed polymeric material.

When the composite membrane material is impregnated with said formedpolymeric material said composite membrane material may be a fabric or amicroporous membrane. When said composite membrane material is a fabric,the method may include a step of contacting the fabric with saidcomposite formulation in order to impregnate said fabric. Thereafter,the method includes providing conditions for removal of said solventformulation, leaving said formed polymeric material in pores of saidfabric.

If said composite membrane material is a crystalline or crystallisablepolymeric material for example having moieties I, II and/or III and/orpreferred repeat units IV, IV*, V and V*, then on contact with saidcomposite formulation, the composite membrane material may plasticiseand, in some circumstances, the crystallinity of the material may beincreased.

When said composite membrane material is a microporous membrane, themethod may include the step of contacting the microporous membrane withsaid composite formulation in order to impregnate said micoporousmembrane. Thereafter, the method includes providing conditions forremoval of said solvent formulation leaving said formed polymericmaterial in pores in said microporous membrane.

When said composite membrane material is a microporous membrane,preparation of the membrane may include a step of contacting a compositemembrane material with a solvent formulation comprising a solubilizingsolvent which solubilizes, to some degree, the composite membranematerial. Subsequently, the method preferably includes the step ofcontacting the composite membrane material with a second, suitablyaqueous, phase inversion solvent which is arranged to cause phaseinversion, thereby resulting in said composite membrane material beingrendered porous.

One example of a composite membrane may comprise a microporous membraneof polyetherketone which may be prepared by casting a solution ofpolyetherketone in sulphuric acid followed by phase inversion using anaqueous solvent, especially water. Then, said microporous membrane maybe impregnated with a composite formulation for example comprising afirst ion-conducting polymeric material in a said solvent formulationfor example comprising an acetone/water mixture. Advantageously, saidsolvent formulation may increase the crystallinity of thepolyetherketone.

After impregnation of a microporous membrane as described above, thearrangement may be post-treated, suitably so as to produce asubstantially continuous film of said first ion-conducting polymericmaterial on the composite membrane material.

When the composite membrane material is an ion-conducting materialeither said composite membrane material or said formed polymericmaterial may act as a support for the other one of either the formedpolymeric material or membrane material.

When the composite membrane material or said first ion-conductingpolymeric material acts as a support for the other, then the materialwhich is to provide the support may be rendered microporous as describedabove and the other material impregnated therein.

Any suitable conditions for removal of said solvent formulation in step(v) of said method may be provided. Conveniently, said formulation isremoved by evaporation in an environment arranged at a temperaturegreater than ambient temperature, for example at a temperature of atleast 50° C. and, preferably, less than 150° C.

A said formed polymeric material as described herein may be used in fuelcells (e.g. Hydrogen Fuel Cells or Direct Methanol Fuel Cells) orelectrolysers. Said formed polymeric material may also be used infiltration (as parts of filtration membranes), for example inultrafiltration, microfiltration or in reverse osmosis.

The following further utilities for said formed polymeric material arealso contemplated:

-   1. Proton exchange membrane based water electrolysis, which involves    a reverse chemical reaction to that employed in hydrogen/oxygen    electrochemical fuel cells.-   2. Chloralkali electrolysis, typically involving the electrolysis of    a brine solution to produce chlorine and sodium hydroxide, with    hydrogen as a by-product.-   3. Electrode separators in conventional batteries due to the    chemical inertness and high electrical conductivity of the composite    membranes.-   4. Ion-selective electrodes, particularly those used for the    potentiometric determination of a specific ion such as Ca²⁺, Na⁺, K⁺    and like ions. The formed polymeric material could also be employed    in a sensor material for humidity sensors, as the electrical    conductivity of an ion exchange membrane varies with humidity.-   5. Ion-exchange material for separations by ion-exchange    chromatography. Typical such applications are deionization and    desalination of water (for example, the purification of heavy metal    contaminated water), ion separations (for example, rare-earth metal    ions, trans-uranium elements), and the removal of interfering ionic    species.-   6. Ion-exchange membranes employed in analytical preconcentration    techniques (Donnan Dialysis). This technique is typically employed    in analytical chemical processes to concentrate dilute ionic species    to be analysed.-   7. Ion-exchange membranes in electrodialysis, in which membranes are    employed to separate components of an ionic solution under the    driving force of an electrical current. Electrolysis applications    include the industrial-scale desalination of brackish water,    preparation of boiler feed make-up and chemical process water,    de-ashing of sugar solutions, deacidification of citrus juices,    separation of amino acids, and the like.-   8. Membranes in dialysis applications, in which solutes diffuse from    one side of the membrane (the feed side) to the other side according    to their concentration gradient. Separation between solutes is    obtained as a result of differences in diffusion rates across the    membrane arising from differences in molecular size. Such    applications include hemodialysis (artificial kidneys) and the    removal of alcohol from beer.-   9. Membranes in gas separation (gas permeation) and pervaporation    (liquid permeation) techniques.-   10. Bipolar membranes employed in water splitting and subsequently    in the recovery of acids and bases from waste water solutions.

The most preferred use of said formed polymeric material is as a part ofor substantially the whole of a polymer electrolyte membrane in a fuelcell.

According to a second aspect of the invention, there is provided amethod of preparing a membrane electrode assembly, the method includingassociating a catalyst material with a polymeric material prepared in amethod according to the first aspect. Said polymeric material may be acomponent of a composite membrane as described according to said firstaspect.

According to a third aspect of the invention, there is provided amembrane electrode assembly prepared as described according to thesecond aspect.

According to a fourth aspect of the invention, there is provide a methodof making a fuel cell, the method including associating a polymericmaterial and/or a membrane electrode assembly as described according tothe first, second or third aspects with other components of said fuelcell.

According to a fifth aspect of the present invention, there is provideda fuel cell (e.g. a Hydrogen Fuel Cell or Direct Methanol Fuel Cell)incorporating a polymeric material and/or membrane electrode assembly asdescribed according to the first, second, third and fourth aspects ofthe present invention.

Polymers having units I, II, III, IV, IV*, V and/or V* described hereinmay be prepared by:

(a) polycondensing a compound of general formula

with itself wherein Y¹ represents a halogen atom or a group -EH and Y²represents a halogen atom or, if Y¹ represents a halogen atom, Y²represents a group E′H; or

(b) polycondensing a compound of general formula

with a compound of formula

and/or with a compound of formula

wherein Y¹ represents a halogen atom or a group -EH (or -E′H ifappropriate) and X¹ represents the other one of a halogen atom or group-EH (or -E′H if appropriate) and Y² represents a halogen atom or a group-E′H and X² represents the other one of a halogen atom or a group -E′H(or -EH if appropriate).

(c) optionally copolymerizing a product of a process as described inparagraph (a) with a product of a process as described in paragraph (b);

wherein the phenyl moieties of units VI, VII and/or VIII are optionallysubstituted; the compounds VI, VII and/or VIII are optionallysulphonated; and Ar, m, w, r, s, z, t, v, G, E and E′ are as describedabove except that E and E′ do not represent a direct link;

the process also optionally comprising sulphonating and/or cross-linkinga product of the reaction described in paragraphs (a), (b) and/or (c) toprepare said polymer.

In some situations, the polymer prepared, more particularly phenylgroups thereof, may be optionally substituted with the groupshereinabove described after polymer formation.

Preferably, where Y¹, Y², X¹ and/or X² represent a halogen, especially afluorine, atom, an activating group, especially a carbonyl or sulphonegroup, is arranged ortho- or para- to the halogen atom.

Preferred halogen atoms are fluorine and chlorine atoms, with fluorineatoms being especially preferred. Preferably, halogen atoms are arrangedmeta- or para- to activating groups, especially carbonyl groups.

Where the process described in paragraph (a) is carried out, preferablyone of Y¹ and Y² represents a fluorine atom and the other represents anhydroxy group. More preferably in this case, Y¹ represents a fluorineatom and Y² represents an hydroxy group. Advantageously, the processdescribed in paragraph (a) may be used when Ar represents a moiety ofstructure (i) and m represents 1.

When a process described in paragraph (b) is carried out, preferably, Y¹and Y² each represent an hydroxy group. Preferably, X¹ and X² eachrepresent a halogen atom, suitably the same halogen atom.

The polycondensation reaction described is suitably carried out in thepresence of a base, especially an alkali metal carbonate or bicarbonateor a mixture of such bases. Preferred bases for use in the reactioninclude sodium carbonate and potassium carbonate and mixtures of these.

The identity and/or properties of the polymers prepared in apolycondensation reaction described may be varied according to thereaction profile, the identity of the base used, the temperature of thepolymerisation, the solvent(s) used and the time of the polymerisation.Also, the molecular weight of a polymer prepared may be controlled byusing an excess of halogen or hydroxy reactants, the excess being, forexample, in the range 0.1 to 5.0 mole %

In a polymer prepared in a said polycondensation reaction involvingcompounds of general formula VI, VII, and VIII, moieties of generalformula VI, VII, and VIII (excluding end groups Y¹, Y², X¹ and X²) maybe present in regular succession (that is, with single units of one saidmoiety, separated by single units of another said moiety or moieties),or semi-regular succession (that is, with single units of one saidmoiety separated by strings of another moiety or moieties which are notall of the same length) or in irregular succession (that is, with atleast some multiple units of one moiety separated by strings of othermoieties that may or may not be of equal lengths). The moietiesdescribed are suitably linked through ether or thioether groups.

Also, moieties in compounds VI, VII and VIII arranged between a pair ofspaced apart —O— atoms and which include a -phenyl-SO₂ or -phenyl-CO—bonded to one of the —O— atoms may, in the polymer formed in thepolycondensation reaction, be present in regular succession,semi-regular succession or in irregular succession, as describedpreviously.

In any sampled polymer, the chains that make up the polymer may be equalor may differ in regularity from one another, either as a result ofsynthesis conditions or of deliberate blending of separately madebatches of polymer.

Compounds of general formula VI, VII and VIII are commercially available(eg from Aldrich U.K.) and/or may be prepared by standard techniques,generally involving Friedel-Crafts reactions, followed by appropriatederivatisation of functional groups. The preparations of some of themonomers described herein are described in P M Hergenrother, B J Jensenand S J Havens, Polymer 29, 358 (1988), H R Kricheldorf and U Delius,Macromolecules 22, 517 (1989) and P A Staniland, Bull, Soc, Chem, Belg.,98 (9–10), 667 (1989).

Where compounds VI, VII and/or VIII are sulphonated, compounds offormulas VI, VII and/or VIII which are not sulphonated may be preparedand such compounds may be sulphonated prior to said polycondensationreaction.

Sulphonation as described herein may be carried out in concentratedsulphuric acid (suitably at least 96% w/w, preferably at least 97% w/w,more preferably at least 98% w/w; and preferably less than 98.5% w/w) atan elevated temperature. For example, dried polymer may be contactedwith sulphuric acid and heated with stirring at a temperature of greaterthan 40° C., preferably greater than 55° C., for at least one hour,preferably at least two hours, more preferably about three hours. Thedesired product may be caused to precipitate, suitably by contact withcooled water, and isolated by standard techniques. Sulphonation may alsobe effected as described in U.S. Pat. No. 5,362,836 and/or EP0041780.

When said first polymeric material comprises a first crystalline orcrystallisable unit, a second ion-exchange unit and a third amorphousunit as described above, the process may comprise:

-   polycondensing a compound of formula    X¹-BM-X²   IXXX-   with a compound of formula    Y¹—SU—Y²   XXX-    and with a compound of formula    Y¹—XT-Y²   XXXI-    and with a compound of formula    Z¹-AM-Z²   XXXII    thereby to prepare a copolymer, wherein Y¹ represents a halogen atom    or a group -EH (or -E′H if appropriate) and X¹ represents the other    one of a halogen atom or group -EH (or -E′H if appropriate), Y²    represents a halogen atom or a group —E′H and X² represents the    other one of a halogen atom or a group -E′H (or -EH if appropriate)    and Z¹ and Z² represent a halogen atom or a group -EH (or E′H if    appropriate);    and wherein BM represents part of a base monomer, SU represents part    of a moiety which is functionalised or can be functionalised    (suitably independently of other moieties in the copolymer) to    provide ion-exchange sites, XT represents a part of a crystalline or    crystallisable moiety and AM represents part of an amorphous moiety.

The polycondensation reaction may be carried out as described above.

First crystalline/crystallisable units of formula XVI described aboveare preferably prepared by reaction of a dihydroxy-containing monomerwith a di-halogen-containing monomer provided that the monomers includeonly single phenyl moieties (i.e. no multi-phenylene moieties) separatedby —CO— or —O— groups between the halogen or hydroxy end groups thereof.Second ion-conducting units of formula XVII described above arepreferably prepared by reaction of dihydroxybiphenyl, dihydroxybenzeneor dihydroxynaphthalene with a halogen-containing monomer followed bypost-sulphonation of the units. Optional third units of formula XVIIImay be prepared by reaction of 4,4′-dihydroxydiphenylsulphone or2,4-dihydroxybenzophenone with a halogen-containing monomer.

Preferred combinations of monomers for preparation of polymers which,after sulphonation, are crystalline/crystallisable are detailed inTables 1 and 2 is below wherein the * in each row indicates the monomersthat can be used to prepare preferred polymers. In the tables, thefollowing abbreviations are used:

-   BP 4,4′dihydroxybiphenyl-   HQ hydroquinone-   DHN dihydroxynaphthalene (Examples include 1,5-; 1,6-; 2,3-; and    2,7-)-   BDF 4,4′-difluorobenzophenone.-   DCDPS 4,4′-dichlorodiphenylsulphone.-   DKDH 1,4-bis-(4-hydroxybenzoyl)benzene.-   DKDF 1,4-bis-(4-fluorobenzoyl)benzene.-   DHB 4,4′-dihydroxybenzophenone.-   2,4-DHB 2,4-dihydroxybenzophenone.-   Bis-S 4,4′-dihydroxydiphenylsulphone.

TABLE 1 BP HQ DHN BDF DKDF DHB 2,4-DHBBis-S * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * **

TABLE 2 BP HQ DHN BDF DKDF DKDH 2,4-DHBBis-S * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * **

More complex combinations comprising the combinations in Table 1together with one or more additional monomer may be selected, fromexample, BP+BDF+Bis-S+DCDPS+DHB.

The invention extends to any novel polymer, whether provided withion-exchange sites or otherwise, described herein. The invention extendsto any novel polymer, pre- or post-sulphonated prepared from themonomers described in Tables 1 and 2.

Details on the preparation of polymers and processes for the preparationof membranes therefrom are provided in WO00/15691, PCT/GB00/03449,GB0031209.0, GB0031208.2 and GB0031207.4 and the contents of theaforesaid are incorporated herein by reference.

Unless otherwise stated, all chemicals referred to hereinafter were usedas received from Sigma-Aldrich Chemical Company, Dorset, U.K.

Specific embodiments of the invention will now be described, by way ofexample.

EXAMPLE 1a

A 700 ml flanged flask fitted with a ground glass Quickfit lid,stirrer/stirrer guide, nitrogen inlet and outlet was charged with4,4′-difluorobenzophenone (89.03 g, 0.408 mole), 4,4′-dihydroxybiphenyl(24.83 g, 0.133 mole) 4,4′-dihydroxydiphenylsulphone (66.73 g, 0.267mole), and diphenysulphone (332 g) and purged with nitrogen for over 1hour. The contents were then heated under a nitrogen blanket to between140 and 150° C. to form an almost colourless solution. While maintaininga nitrogen blanket, dried sodium carbonate (42.44 g, 0.4 mole) andpotassium carbonate (1.11 g, 0.008 mole) were added. The temperature wasraised gradually to 315° C. over 3 hours then maintained for 0.5 hours.

The reaction mixture was allowed to cool, milled and washed with acetoneand water. The resulting polymer was dried in an air oven at 120° C. Thepolymer had a melt viscosity at 400° C., 1000 sec⁻¹ of 0.62 kNsm⁻².

EXAMPLE 1b

A 700 ml flanged flask fitted with a ground glass Quickfit lid,stirrer/stirrer guide, nitrogen inlet and outlet was charged with4,4′-difluorobenzophenone (89.03 g, 0.408 mole), 4,4′-dihydroxybiphenyl(24.83 g, 0.133 mole), 4,4′-dihydroxydiphenylsulphone (53.65 g, 0.213mole), 4,4′-dihydroxybenzophenone (11.37 g, 0.053 mole) anddiphenysulphone (332 g) and purged with nitrogen for over 1 hour. Thecontents were then heated under a nitrogen blanket to between 140 and150° C. to form an almost colourless solution. While maintaining anitrogen blanket, dried sodium carbonate (43.24 g, 0.408 mole) wasadded. The temperature was raised gradually to 320° C. over 3 hours thenmaintained for 1.5 hours.

The reaction mixture was allowed to cool, milled and washed with acetoneand water. The resulting polymer was dried in an air oven at 120° C. Thepolymer had a melt viscosity at 400° C., 1000 sec⁻¹ of 0.53 kNsm⁻².

EXAMPLE 1c

The polymerisation procedure of Example 1b was followed, for 1c, exceptthat the copolymer was prepared by varying the mole ratios of thehydroxy-containing reactants.

A summary of the mole ratios and MV are detailed in Table A below.

EXAMPLES 1d and 1e

The polymerisation procedure of Example 1a and 1b were followed, for 1dand 1e respectively, except that copolymers were prepared by varying themole ratios of the hydroxy-containing reactants.

A summary of the mole ratios and MVs for the aforementioned examples aredetailed in the Table A below. BDF, BP, DHB and Bis-S have the meaningsdescribed above.

TABLE A Polymer composition (mole ratio) MV Example BDF BP DHB Bis-S(kNsm⁻²) 1a 1.02 0.33 — 0.67 0.62 1b 1.02 0.33 0.133 0.536 0.53 1c 1.020.33 0.268 0.402 0.38 1d 1.02 0.40 — 0.6 0.26 1e 1.02 0.40 0.24  0.360.60

EXAMPLE 2 General Sulphonation Procedure

The polymers of Examples 1a–1e were sulphonated by stirring each polymerin 98% sulphuric acid (3.84 g polymer/100 g sulphuric acid) for 21 hoursat 50° C. Thereafter, the reaction solution was allowed to drip intostirred deionised water. Sulphonated polymer precipitated asfree-flowing beads. Recovery was by filtration, followed by washing withdeionised water until the pH was neutral and subsequent drying. Ingeneral, titration confirmed that 100 mole % of the biphenyl units hadsulphonated, giving one sulphonic acid group, ortho to the etherlinkage, on each of the two aromatic rings comprising the biphenyl unit.

EXAMPLE 3a Membrane Fabrication

Membranes were produced from the polymers from Examples 1a to 1e aftersulphonation as described in Example 2 by dissolving the polymers in thesolvent systems at the concentrations and at the temperature asdescribed in Table B below. The concentrations used were approximatelyequal to the maximum concentration to which a particular polymer couldbe dissolved in a specified solvent system. Table B details resultsusing NMP alone for the purposes of comparison with other solventsystems described. In the case of the solvent systems which include a“*”, the particular polymer was dissolved in the solvent system shownand, thereafter, 5% v/v NMP was added to the solution prior to casting.

The homogeneous solutions were cast onto clean glass plates and thendrawn down to give 400 micron films, using a Gardner Knife. The solventwas then evaporated at the temperature as described in Table B.

EXAMPLE 3b Boiling Water Uptake

The following general procedure was followed to determine the BoilingWater Uptake of the membranes prepared.

5 cm×5 cm samples of membranes were selected. The thickness of thesamples was related to the concentration of polymers in the solventsystems used to cast the membranes. The membranes were separatelyimmersed in boiling deionised water (500 ml) for 60 mins, removed anddried quickly with lint-free paper to remove surface water, weighed,dried in an oven at 50° C. for 1 day, allowed to cool to ambienttemperature in a desiccator then weighed quickly. The % water-uptake wascalculated as described below:

${{\%\mspace{20mu}{Water}} - {uptake}} = {\frac{{{Wet}\mspace{14mu}{Weight}} - {{Dry}\mspace{14mu}{Weight}}}{{Dry}\mspace{14mu}{Weight}} \times 100}$

Results for membranes assessed are provided in the Table B.

The following abbreviations are used in the Table:

-   NMP—N-methylpyrrolidone-   DCM—dichloromethane-   MeOH—methanol-   DMAC—dimethylacetamide-   THF—tetrahydrofuran-   MEK—methyl ethyl ketone-   EA—ethyl acetate-   CHX—cyclohexanone

TABLE B Polymer from specified example after Boiling sulphonationMeasured Dissolution Evaporation Water as described Theoretical EW bySolvent Solvent ratio Conc Temperature Temperature Uptake in example 2EW titration System (v/v) % w/w (° C.) (° C.) (%) 1a 690 660 NMP 1 15 RT100 165 1a — — Water/Ace* 0.5:0.5 15 RT 80 170 1b 683 663 NMP 1 15 RT100 160 1b — — Water/DCM/ 0.4:0.5:0.1 10 40–50 70 60 MeOH* 1b — —Water/THF* 0.5:0.5 10 70–80 80 71 1b — — Water/THF* 0.7:0.3 16 70–80 80140 1b — — Water/MEK/ 0.4:0.5:0.1 10 80–90 80 75 MeOH* 1b — — Water/Ace/0.4:0.4:0.2 7.5 60–70 80 74 EA* 1b — — Water/Ace* 0.35:0.65 10 60–70 8088 1b — — Water/Ace* 0.50:0.50 10 60–70 80 102 1b — — Water/Ace/0.475:0.475:0.05 10 60–70 80 105 NMP 1b — — Water/Ace/ 0.475:0.475:0.0510 60–70 80 99 DMAc 1b — — water/Ace/MEK* 0.4:0.1:0.5 7.5 50–60 80 88 1b— — water/CHX/MeOH* 0.4:0.5:0.1 7.5 60–70 80 86 1b — — water/EA/0.25:0.5:0.25 6 RT 80 89 MeOH* 1c 676 685 NMP 1 15 80 100 100 1c — —water/ 0.5:0.5 10 60–70 80 77 Acetone* 1c — — Water/Ace/NMP0.475:0.475:0.05 10 60–70 80 74 1c — — Water/Ace/DMAc 0.575:0.375:0.0510 60–70 80 85 1c — — water/Ace/MEK* 0.65:0.25:0.1 12 70–80 80 79 1c — —water/THF* 80:20 15 70–70 80 79 1d 583 602 NMP 1 15 RT 100 520 1d — —Acetone/ 0.5:0.5 10 RT 80 560 water* 1e 564 564 NMP 1 15 RT 100 550 1e —— Ace/water* 0.5:0.5 10 60–70 80 154 1e — — THF/water* 0.5:0.5 10 70–8080 143

EXAMPLE 4 Determination of the Crystallinity Index Values of Polymers byWide Angle X-Ray Scattering (WAXS)

Crystallinity can be quantified, in one method, by defining a“crystallinity index” for measurements made by Wide Angle X-rayScattering (WAXS). This approach defines the measurement in relation tothe WAXS pattern. The measured area of crystalline peaks in the WAXSpattern is taken as a percentage of the total crystalline and amorphousscatter over a chosen angular range of the pattern. Crystallinity indexshould, to a first approximation, be proportional to crystallinity forbroadly similar polymer materials. It is constrained to be zero whencrystallinity is zero and 100% when crystallinity is 100%.

Membranes of the sulphonated polymers from Examples 1a, 1b and 1c aftersulphonation as described in Example 2 were cast from NMP andacetone/water (0.5:0.5)as described in Example 3a and then examined byWAXS as described below.

The membranes were analysed using a Siemens D5000 X-ray diffractometerwith Cu K-alpha radiation and a Kevex energy dispersive detector.Measurements were made from a single membrane sheet mounted insymmetrical reflection geometry. A programmable divergence slit was usedto maintain a constant irradiated region of the specimen surface 6 mmlong over a 2-theta measurement range of 10–49°.

The WAXS pattern of membranes made from the sulphonated polymer fromExample la cast from NMP and acetone/water respectively and a membranemade from the sulphonated polymer from Example 1b cast from NMPexhibited only broad amorphous scatter, whereas the patterns formembranes from Example 1c material cast from NMP and Examples 1b and 1cmaterial cast from acetone/water exhibited crystalline peaks in additionto amorphous bands.

The measured WAXS patterns were analysed by first making a backgroundcorrection, subtracting the corresponding WAXS pattern from a blankspecimen holder. The resulting patterns were fitted by a combination ofa pattern measured from a similar but amorphous membrane film and a setof peaks (at approximately 18.8, 20.8, 22.9, 29.1 and 40.0° 2-theta)corresponding to those observed in the more crystalline membranes. Thecrystallinity index was calculated as the total area fitted by thesepeaks taken as a percentage of the combined area of the fitted peaks andthe fitted amorphous pattern.

Crystallinity Index Sulphonated polymer from Example (%) 1a cast fromNMP 0 1a cast from acetone/water (0.5:0.5) 0 1b cast from NMP 0 1b castfrom acetone/water (0.5:0.5) 0.5 1c cast from NMP 2 1c cast fromacetone/water (0.5:0.5) 7.6

The reader's attention is directed to all papers and documents which arefiled concurrently with or previous to this specification in connectionwith this application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or stepsare mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings), may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention is not restricted to the details of the foregoingembodiment(s). The invention extend to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

Any feature of any aspect of any invention or embodiment describedherein may be combined with any feature of any aspect of any otherinvention or embodiment described herein.

1. A method of preparing an ion-conducting polymeric material in adesired form (hereinafter “said formed polymeric material”), the methodcomprising: (i) selecting a first ion-conducting polymeric materialwhich is crystalline or crystallisable, wherein said firstion-conductive polymeric material is one having a moiety of formula:

 and/or a moiety of formula

 and/or a moiety of formula

 wherein at least some of the units I, II and/or III are functionalizedto provide ion-exchange sites, wherein the phenyl moieties in units I,II, and III are independently optionally substituted and optionallycross-linked; and wherein m, r, s, t, v, w and z independently representzero or a positive integer, E and E′ independently represent an oxygenor a sulphur atom or a direct link, G represents an oxygen or sulphuratom, a direct link or a —O—Ph—O— moiety where Ph represents a phenylgroup and Ar is selected from one of the following moieties (i)* or (i)to (x) which is bonded via one or more of its phenyl moieties toadjacent moieties; (ii) selecting a solvent formulation which candissolve said first ion-conducting polymeric material and increase itscrystallinity, wherein said formulation includes a first solvent partwhich is water; (iii) preparing a composite formulation in a processwhich includes dissolving first ion-conducting polymeric material insaid solvent formulation; (iv) forming said composite formulation into adesired form; (v) providing conditions for removal of said solventformulation from said form described in (iv) thereby to prepare saidformed polymeric material.
 2. A method according to claim 1, whereinsaid solvent formulation in which said first ion-conducting polymericmaterial is dissolved includes a second solvent part.
 3. A methodaccording to claim 2, wherein said second solvent part is an organicsolvent.
 4. A method according to claim 3, wherein said second solventpart has a boiling point at atmospheric pressure of greater than −30° C.and less than 200° C.
 5. A method according to claim 2, wherein saidsecond solvent part is able to form a dipole-dipole interaction with thefirst polymeric material.
 6. A method according to claim 2, wherein saidsecond solvent part includes a ketone, ether or haloalkyl group or anunsaturated ring structure.
 7. A method according to claim 2, whereinsaid second solvent part is a polar aprotic solvent.
 8. A methodaccording to claim 2, wherein said second solvent part is selected frombenzene, toluene, dichloromethane, tetrahydrofuran, cyclopentanone,acetone, 1,3-dichloropropane, chlorobenzene, tetrafluoroethane,diethylketone, methylethyl ketone, cyclohexanone and ethylbenzene.
 9. Amethod according to claim 2, wherein said second solvent part isselected from acetone, tetrahydrofuran and dichloromethane.
 10. A methodaccording to claim 2, wherein said second solvent part is acetone.
 11. Amethod according to claim 1, wherein said first polymeric material issulphonated.
 12. A method according to claim 1, wherein said firstpolymeric material is a homopolymer having a repeat unit of generalformula

or a homopolymer having a repeat unit of general formula

or a homopolymer having a repeat unit of general formula

or a homopolymer having a repeat unit of general formula

or a random or block copolymer of at least two different units of IV,IV*, V and/or V* provided that repeat units (or parts of repeat unit)are functionalised to provide ion-exchange sites; wherein A, B, C and Dindependently represent 0 or 1 and E, E′, G, Ar, m, r, s, t, v, w, and zE′ independently represent an oxygen or a sulphur atom or a direct link,G represents an oxygen or sulphur atom, a direct link or a —O—Ph—O—moiety where Ph represents a phenyl group and Ar is selected from one ofthe following moieties (i)* or (i) to (x) which is bonded via one ormore of its phenyl moieties to adjacent moieties.
 13. A method accordingto claim 1, wherein said first ion-conducting polymeric materialincludes a first crystalline or crystallisable unit which is of generalformula IV, IV*, V or V* as defined above, provided said unit iscrystalline or crystallisable; and a second ion-exchange unit of formulaIV, V, IV* or V* as defined above, which includes ion-exchange sites.14. A method according to claim 13, wherein said first crystalline orcrystallisable unit includes a repeat unit of formula

wherein n1, n2, n3 and n4 independently represent 0 or 1 provided thatthe sum of n1, n2, n3 and n4 is at least 2 and that when n2 is 1 atleast one of n3 and n4 is
 1. 15. A method according to claim 13, whereinsaid second ion-conducting unit is of formula

wherein IEU refers to a unit which incorporates ion-exchange sites andn⁵, n⁶ and n⁷ represent 0 or 1 provided that the sum of n⁵, n⁶ and n⁷ isat least
 1. 16. A method according to claim 1, wherein said firstpolymeric material includes at least some ketone moieties in thepolymeric chain.
 17. A method according to claim 1, wherein theequivalent weight (EW) of said ion-conductive polymeric material is lessthan 850 g/mol and is greater than 300 g/mol.
 18. A method according toclaim 2, wherein the ratio of the volume of said first solvent part tothe volume of said second solvent part in said solvent formulation is inthe range 0.2 to
 5. 19. A method of preparing a membrane electrodeassembly, the method including associating a catalyst material with apolymeric material prepared in a method according to claim 1.